1. Field of the Invention
The present invention relates to a method of generating a spray that is suitable for a fuel injection valve for, for example, an internal combustion engine (hereinafter referred to as an “engine”). The invention also relates to a fluid injection valve and a spray generation apparatus.
2. Description of the Related Art
In recent years, research and development have been carried out actively in the field of engines for vehicles such as automobiles to reduce emission gas during engine cold time through atomization of fuel spray and to improve fuel consumption through improving combustibility.
The fuel injection system of gasoline engine is classified into two systems, a port injection system and an in-cylinder injection system.
The important three elements to establish the combustion concept of the in-cylinder injection system are the spray specifications (including the injection position), the in-cylinder air flow movement, and the combustion chamber shape.
It is only after the matching of these elements becomes possible that the combustion concept can be established. However, because the internal pressure of the cylinder and the in-cylinder air flow movement change depending on the engine rotational frequency or the load, and the fuel injection amount and the injection timing are changed correspondingly, the spray profile and spray behavior in the cylinder also change accordingly. Therefore, it is a difficult task to match the three elements and at the same time to prevent the adherence of sprayed fuel to the cylinder inner wall surface under various operating conditions, with the constraints of the layout in the engine room.
Likewise, in the port injection system, the spray specifications (including the injection position), the intake air flow movement, and the intake port shape are the three elements for achieving the optimum injection system, like the three elements for establishing the combustion concept of the in-cylinder injection system.
The common port injection system has a configuration in which, in the case of two intake valves, two-direction sprays corresponding thereto are used to inject the fuel targeting the intake valves. Moreover, development has been carried out to achieve a spray shape or a spray direction targeting such that the spray does not adhere to the intake port wall surface by improving atomization of the spray. However, the intake port shape and the accompanying intake air flow movement cannot necessarily be optimized because of the constraints of the layout in the engine room. Therefore, no technique for achieving both the improvement in the atomization of the spray and the spray shape/injection direction targeting has been disclosed clearly.
Furthermore, there are many middle or large-sized motorcycles in which the fuel injection aiming at the intake valves cannot be carried out because of the constraints of the lay-out. It is not necessarily clear what type of injection system concept is optimum in that case. Therefore, a future development effort has been expected.
Moreover, small-sized motorcycles, outboard engines, and multi-purpose engines are in a transitional period from the carburetor to the port injection system, and many of them have an engine with one intake valve. In reality, because of the problems associated with the lay-out, they have an injection configuration such that the intake valve may or may not be targeted by a unidirectional spray (one spray). However, it is clear that the emission gas reduction and the fuel consumption improvement will be demanded more and more in the future, so the optimum specifications with reduced system costs will be required.
As described above, examples of the parameters used for the matching in the conventional port injection system of a gasoline engine are, in the case of the two-spray specification, the spray angle of each spray, the injection amount distribution image in the cross section perpendicular to the injection direction, the injection angle (narrow angle) of the two sprays, and a representative droplet diameter at a certain point in the spray.
More specifically, the cross-sectional shape of each spray perpendicular to the injection direction forms a substantially circular shape or a substantially elliptical shape. While the basic specification of the injection amount distribution thereof is set to be a substantially solid conical shaped distribution having a peak almost at the center, the improvement of atomization is attempted as needed. In reality, when the one is given priority, the other one cannot be controlled because the level of atomization and the spray angle have a correlation with each other.
The reason why the peak of the injection amount distribution is formed almost at the center is that the injection directions from the respective orifices are aimed at the direction in which they gather. For this reason, the distribution ratio tends to be relatively high in the center portion.
In the case of one spray specification as well, the related portion in the just-described content may be applied.
In view of these problems, various proposals have been made concerning nozzle or spray, as in Patent Documents 1 to 6, for example.